Saccharomyces cerevisiae harbor an autonomously replicating 2-.mu. plasmid containing the gene FLPy. FLPy encodes the protein, FLP, a site-specific recombinase acting at defined FLP-recognition targets, FRTs.
Like the cre/lox bacterial system, the yeast FLP/FRT system has been suggested as providing a useful and efficient method for inserting or excising genes in a genome of choice. However, in practice, the yeast FLP nucleic acid sequence (FLPy) does not efficiently express active recombinase in plant cells. For example, in experiments with suspension cells and callus, FLP-transformed maize cells produced only a very low frequency of detectable excision events. See, for example, Lyznik et al. (1993) Nucleic Acids Res. 21:969-975 and the Examples below. Furthermore, it has not previously been demonstrated that the FRT/FLP system functions in monocot plants, or that FRT or FLP are inheritable and functional in the progeny of monocot plants.
It would therefore be very beneficial to provide an FLP nucleic acid sequence that would efficiently produce an effective FLP recombinase in monocot plant cells, particularly in maize cells. Such an effective FLP would permit use of FLP recombinase to selectively and reliably modulate gene excision events in a plant cell genome. It would also be very useful to provide monocot plants stably transformed with FRT nucleic acid sequences, FLP nucleic acid sequences, or both, capable of producing high frequency recombination events, which stably transformed plants pass the FRT/FLP nucleic acid sequences and active recombinase to subsequent generations.